Corrosion inhibiting compositions, typically in the form of solutions, suspensions or emulsions are commonly employed in the metal working industry to provide improved corrosion resistance of the metal objects involved. An example of such metal objects is steel cord, which is applied in rubber articles as metal reinforcement. Corrosion of steel cord may occur in the manufacturing process, during storage and transport of the steel cord as well as during and after the application of the steel cord in the rubber articles. In this respect it is remarked that always a certain amount of moisture is present in said rubber articles whereas additional moisture may penetrate the rubber articles by way of diffusion and in particular by way of hair cracks and other imperfections.
In the prior art many corrosion inhibiting compositions have been used. For instance, in DE-A 2.704.190 a method is disclosed for improving the corrosion resistance of steel cord coated with Zn, brass or bronze layer by dipping it just long enough in a sodium nitrite or potassium nitrite solution for moistening to occur and then drying it at a temperature below 150.degree. C.
Another method for providing corrosion protection to steel cord to be embedded in rubber articles like tires is disclosed in JP 02227304 A2. According to said document the tires have interior layers containing water-absorbing polymers and exterior layers of halobutyl rubbers.
Further it is known to apply a corrosion inhibiting composition, comprising specific reaction products like the product 6[2,4-bis(allylamino)-s-triazin-6-ylamino]-2-mercaptobenzothiazole as disclosed in Example 10 (B) of EP 331279 A2 to brass coated steel cord.
As apparent from the above it is known from the prior art to apply corrosion inhibiting compositions to steel cord resulting in an improved corrosion resistance of the treated steel cord. However, such an improvement of the corrosion resistance may result in a considerable loss of the adherence between the steel cord and the rubber comprising the steel cord as a reinforcing means.
U.S. Pat. No. 5,221,490 discloses a rust-preventive lubricant composition useful for zinc-plated steel materials in the form a sheet or strip. The composition of the invention comprises a lubricant component and a rust-inhibiting component with a composition comprising at least one member selected from sulphonates (C.gtoreq.16), carboxylic acids (C.gtoreq.12), and salts of carboxylic acids.
U.S. Pat. No. 4,201,681 discloses a metalworking lubricant composition which is both effective as corrosion inhibitor and as drawing lubricant and which comprises a mineral oil and a barium sulphonate.
GB-A-2 157 310 discloses a lubricating and anti-corrosion composition for treating metal such as steel sheets. The composition comprises a mineral oil, a basic calcium salt of an alkylaryl sulphonic acid, a further anti-corrosion agent and a saturated C.sub.12-18 fatty acid.
JP-A-53-090 454 discloses a steel cord for reinforcement of rubber products coated with brass and with a solution prepared by dissolving a percentage of barium dinonyl naphtalene sulphonate in mineral oil.
In view of the above the invention is directed to a method for avoiding the above disadvantage, i.e. to develop a corrosion inhibiting composition which decreases the level of corrosion of the steel cord and hardly affects the adherence between the reinforcing means made of steel like a tire cord and some types of rubber. Further the invention should particularly relate to compositions which are environmentally acceptable.